FSCK(8)FSCK(8)NAME
fsck - file system consistency check and interactive repair
SYNOPSIS
/usr/etc/fsck -p [ filesystem ... ]
/usr/etc/fsck [ -P ] [ -b block# ] [ -y ] [ -n ] [ filesystem ] ...
DESCRIPTION
The first form of fsck preens a standard set of filesystems or the
specified file systems. It is normally used in the script /etc/rc
during automatic reboot. In this case fsck reads the table /etc/fstab
to determine which file systems to check. It uses the information
there to inspect groups of disks in parallel taking maximum advantage
of i/o overlap to check the file systems as quickly as possible.
Normally, the root file system will be checked on pass 1, other
``root'' (``a'' partition) file systems on pass 2, other small file
systems on separate passes (e.g. the ``d'' file systems on pass 3 and
the ``e'' file systems on pass 4), and finally the large user file
systems on the last pass, e.g. pass 5. Only partitions in fstab that
are mounted ``rw'' or ``rq'' and that have non-zero pass number are
checked.
The system takes care that only a restricted class of innocuous
inconsistencies can happen unless hardware or software failures
intervene. These are limited to the following:
Unreferenced inodes
Link counts in inodes too large
Missing blocks in the free list
Blocks in the free list also in files
Counts in the super-block wrong
These are the only inconsistencies that fsck with the -p option will
correct; if it encounters other inconsistencies, it exits with an
abnormal return status and an automatic reboot will then fail. For
each corrected inconsistency one or more lines will be printed
identifying the file system on which the correction will take place,
and the nature of the correction. After successfully correcting a file
system, fsck will print the number of files on that file system, the
number of used and free blocks, and the percentage of fragmentation.
If sent a QUIT signal, fsck will finish the file system checks, then
exit with an abnormal return status that causes the automatic reboot to
fail. This is useful when you wish to finish the file system checks,
but do not want the machine to come up multiuser.
Without the -p option, fsck audits and interactively repairs
inconsistent conditions for file systems. If the file system is
inconsistent the operator is prompted for concurrence before each
correction is attempted. It should be noted that some of the
corrective actions which are not correctable under the -p option will
result in some loss of data. The amount and severity of data lost may
be determined from the diagnostic output. The default action for each
consistency correction is to wait for the operator to respond yes or
no. If the operator does not have write permission on the file system
fsck will default to a -n action.
Fsck has more consistency checks than its predecessors check, dcheck,
fcheck, and icheck combined.
The following flags are interpreted by fsck.
-P This flag forces fsck to check the disk even if the clean flag is
set on the disk's superblock.
-b Use the block specified immediately after the flag as the super
block for the file system. Block 16 is always an alternate super
block.
-y Assume a yes response to all questions asked by fsck; this should
be used with great caution as this is a free license to continue
after essentially unlimited trouble has been encountered.
-n Assume a no response to all questions asked by fsck; do not open
the file system for writing.
If no filesystems are given to fsck then a default list of file systems
is read from the file /etc/fstab.
Inconsistencies checked are as follows:
1. Blocks claimed by more than one inode or the free list.
2. Blocks claimed by an inode or the free list outside the range of
the file system.
3. Incorrect link counts.
4. Size checks:
Directory size not of proper format.
5. Bad inode format.
6. Blocks not accounted for anywhere.
7. Directory checks:
File pointing to unallocated inode.
Inode number out of range.
8. Super Block checks:
More blocks for inodes than there are in the file system.
9. Bad free block list format.
10. Total free block and/or free inode count incorrect.
Orphaned files and directories (allocated but unreferenced) are, with
the operator's concurrence, reconnected by placing them in the
lost+found directory. The name assigned is the inode number. If the
lost+found directory does not exist, it is created. If there is
insufficient space its size is increased.
Checking the raw device is almost always faster.
FILES
/etc/fstab contains default list of file systems to check.
DIAGNOSTICS
The diagnostics produced by fsck are fully enumerated and explained in
Appendix A of ``Fsck - The UNIX File System Check Program'' (SMM:5).
SEE ALSOfstab(5), fs(5), newfs(8), mkfs(8), crash(8V), reboot(8)BUGS
There should be some way to start a fsck -p at pass n.
4th Berkeley Distribution May 21, 1986 FSCK(8)